The present invention relates generally to charging apparatus for introducing raw materials into a glass melting furnace and, more particularly, to so-called blanket batch chargers, of the type disclosed in U.S. Pat. Nos. 3,780,889 and 4,197,109 to Frazier et al., and commonly owned with the present invention.
A continuous furnace used for the manufacture of glass typically comprises a large rectangular tank in which the molten bath of glass is contained. A raw batch mixture is continuously introduced into the rear of the furnace by batch charging apparatus of the type mentioned above. At the feed end of the furnace, the batch material is first melted in a melting zone, proceeds to a central zone, and then to a fore hearth region where the molten glass is removed for formation into the desired finished product, such as flat glass or other shapes. The quality of the glass product is largely dependent upon the uniformity of the melt. Furnace efficiency may vary considerably, depending upon the rate of batch feeding and the manner in which the raw batch material is introduced into the furnace. The charging end of the glass furnace typically includes a structure having a charging bay generally referred to in the art as the "doghouse". This furnace structure includes a suspended wall set inwardly from a lower rear wall of the charging bay, leaving an open or semi-open trough therebetween, defining the so-called doghouse across a substantial part of the full width of the furnace. This width varies, and in present furnace structures, can be on the order of 20 to 30 feet in width.
The doghouse provides a downwardly extending open area above the level of the molten glass into which the mixture of glass forming ingredients, or raw batch, is charged. The raw batch material initially floats on the molten glass and melts as it moves forward into the furnace.
The batch charger disclosed in U.S. Pat. No. 3,780,889 has a charger plate that downwardly extends into the exposed area of the doghouse and reciprocates in a direction along the long axis of the furnace. The charger plate is positioned beneath a hopper chute such that as the charger plate moves forward from a retracted limit of travel, raw batch material from the hopper chute is deposited in a layer on the charger plate. Simultaneously, the nose or forward edge of the charger plate pushes a previously deposited layer of the floating batch under the suspended wall at the end of the doghouse into the melting zone of the furnace. As the charger plate moves rearwardly, the layer of batch material then residing on the charger plate is obstructed by a sand seal device at the rear of the hopper from being carried rearwardly and is moved off the charger plate to fall over the nose into the open area of the furnace from which the previous charge has just been cleared. This reciprocating cycle is continuously repeated to maintain a substantially constant level of molten glass in the furnace as the melt is removed at the fore hearth region.
It should be noted that typical glass batch feeders in present day glass producing furnaces are quite massive and difficult to adjust quickly to accommodate operational variables. On furnaces over 20 feet in width, there are typically two charger plates positioned side-by-side. Heretofore, each of these charger plates have employed separate drive motors and drive trains for imparting reciprocating motion thereto. If one of the motors should fail, the entire charger is disabled. A further shortcoming resides in the fact that the charger plates slope downwardly toward the glass level in the furnace at an angle of the order 10 to 15 degrees from the horizontal and it has been customary to individually adjust the angle of each of these plates which has proved to be quite labor intensive. In addition, the lower ends of the hopper chutes in prior devices are provided with a plurality of laterally arrayed adjustable gates. By adjusting these gates up or down with respect to the charger plate, the thickness of the blanket of raw batch deposited on the charger plate can be regulated so that the batch blanket may be thicker at some places across the plate than at others, or vice versa. In this manner, the firing characteristics and currents generated in the furnace bath may be controlled. The adjustment of these gates in prior batch chargers has proven to be troublesome since it is difficult to accurately ascertain by visual observation the exact height of the gate openings.
The final glass quality is also dependent upon the quantity of raw batch material charged into the furnace with each reciprocating stroke of the charger plate. The adjustment of the stroke in prior batch chargers is relatively limited and difficult and time consuming to achieve. It has been observed that continuous melting furnaces of identical construction may exhibit unpredictable variations in performance due to eddy currents, convective currents, flame flow and other factors which influence the quality of the glass and fuel consumption or efficiency in the furnace. It has been observed that a change in the feeding of the batch material results in a noticeable change in fuel efficiency. Because of the individuality of each furnace, it is often necessary to tailor the batch feeder characteristics to maximize the efficiency of a particular furnace. It is, thus, desirable to be able to adjust the stroke length and angular inclination of the charger plate to known values while also adjusting the heights of the plurality of batch gates.
Heretofore, it has proven very difficult, timeconsuming and expensive to make the desired machinery adjustments in large batch chargers without undue interference or downtime in the continuous charging process. Even when such machinery adjustments are possible, it is not always possible or feasible to insure accuracy and duplicity of adjustments due to the types of mechanical linkages and mounting assemblies employed in the prior art.
The problems found in prior art batch chargers are solved by the present invention. The invention provides a batch charger having an adjustable charging plate mechanism, batch gate and charger plate crank assembly which are easily manipulated to permit relatively fast, reproducible and accurate adjustments of each element without costly delays. The present invention also provides a batch charger for glass furnaces having at least two, side-by-side charging plates driven by a versatile power train which permits single or duplex operation by one or both of the drive motors.